Update on current Atu027 Phase I/II trial

8 August 2013 Update on current Atu027 Phase I/II trial : First patient dosed in the Phase IIa part of the study; extension into a multi-center study Silence Therapeutics plc (“Silence” or the “Company”), a leading RNA interference (RNAi) company, provides the following update. Continuation of Phase I/II combination trial on the RNAi therapeutic Atu027 with gemcitabine in first line pancreatic cancer patients (Atu027-I-02/NCT01808638) Following the completion of the safety lead -in part of the stu dy (announced 18 June 2013), Silence has commenced dosing the first patient in a Phase IIa part of the current Atu027-I-02 study. In this study, first-line patients with loco-regionally advanced or metastatic pancreatic cancer are given two different Atu027 treatments on top of the standard gemcitabine regime, the standard chemotherapy for these patients . In pancreatic cancer , the tumor micro - environment is implicated in fostering tumor growth, invasion and metastasis. The novel investigational drug combination aims to attenuate further disease progression by combining the anti-neoplastic activity of gemcitabine with the anti-metastatic action of Atu027. We are taking this opportunity to open additional centers in Germany, which is allowed under the current BfArM approval for human testing of Atu027 . The University Hospital Freiburg (Germany) will become active in the next few weeks. Further centers are being considered. Professor Hubert Blum from University Hospital Freiburg commented: “We are pleased to join the Marienhospital in Herne Germany , which concluded and presented the Phase I safety study of Atu027 as a monotherapy in advanced cancer patients at the American Society of Clinical Oncology meeting in June 2013. This current study looking at the potential anti-metastatic effect of Atu027 in conjunction with a conventional chemotherapy, gemcitabine, is a logical next step in the development of Atu027 . I look forward to seeing this program progress.” Additional information about this trial can be found at www.clinicaltrials.gov. For further information contact: Silence Therapeutics plc +44(0)333 988 0140 Ali Mortazavi, chief executive Tim Freeborn, finance director Nominated advisers N+1 Singer +44(0)20 7496 3000 Shaun Dobson/Jenny Wyllie

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